The return fuel lines leak down and require a long crank to start! ckeck for a small amount of fuel (damp) on the return lines between the back or the motor and fire wall we replase a lot of these.

 

I agree with this. Also if you look in your manual you will see that the vp44 does not like more than 4 psi on cranking. Yes that is 4 psi. not 14 or especially 19 psi. If you call the 1 800 cummins tech line they will tell you the same thing, and they are not sure why, but that is why the computer turns your lift pump on for just a second when you go to start it.
Secondly, if you bump the starter and get improvement in the starting, I would have to think it is air in the system. You can do that 3 or 4 times and it should clear all the air out of the vp44 and take it back to the tank BEFORE you try to start it. Once you try to start it if there is any air that gets into the injector lines it will take a long time to get it out, and it will run really rough.
The place to look for the small amount of fuel at the back of the engine has a brass T fitting and has flat rubber washers inside. Mine leaked a bit for a while, and gave me a hard start condition too, and even after getting the proper washers from Cummins it just wouldn't seal up right so I had to remove it and put a regular T with fuel line and hose clamps on it. Pain in the **** but it solved the problem.
Good luck.

 

Your fuel is leaking off. The cranking over of the engine only restores the fuel and fuel pressure. Could be injectors losing prime, sucking air, but usually the problem in instances like this is the overflow valve not sealing completely and letting the pressure leak off. Another possible culprit is a hairline crack in the fuel line, but if I was a betting man, I'd bet on the injectors or overflow valve. Good luck.